1. Field of the invention
The present invention relates to ramjet vehicles and more particularly to a technique to improve the combustion process in spinning ramjet vehicles.
2. Description of the Prior Art
Projectiles are vehicles that are launches from tanks, artillery pieces or generally, gun tubes. For most applications, gun tubes have helical grooves to provide the launched vehicle with the necessary spinning motion to avoid in-flight dynamic instability that causes the projectile to deviate from its intended path, range and target.
Recently, the concept of air breathing ramjet engines was introduced to the projectile field by using an annular solid fuel grain which internally lines the wall of a tubular projectile body. Results for these projectiles proved to be successful for special size (caliber) category projectiles which are spun about 50,000 revolutions per minute. However, for smaller size (caliber) projectiles, the spin rate necessary for in-flight stability is higher or in the range of 75,000 to 125,000 revolutions per minute. For these smaller size projectiles, preliminary free-flight tests yielded less successful results and inconsistency. A ramjet vehicle is usually launched at high supersonic speeds (5000 ft./sec.). For many projectile applications, this high speed is also coupled with a high rate of spin for some unfinned projectiles. It was found that when using smaller size models, with higher spin rates, the combustion process performance deteriorates. The erratic results were attributed to inconsistent combustion taking place by the solid fuel grain in the smaller size projectiles. These combustion difficulties were attributed to downsizing (scaling) difficulties, shorter flow residence time inside the combustor of the projectile, and higher spin rates. Possible consequences of these higher spin rates are, degrading of the mixing processes between the air and fuel vapor, reduction of the regression rate of the solid fuel grain inside the combustor, and failure of the fuel grain to ignite. Reducing these spin effects on the combustor flow within the projectile body will result in a more reliable and efficient combustion process.
The existing art does not include any spin effect reduction mechanisms for spinning ramjet vehicles. No spin dis-engagement mechanisms are known to exist. The spin dis-engagement of the combustor will reduce the effect of spin on the combustion process which experimentally was found to be damaging to the performance of the vehicle, at high spin rates.
The present invention not only reduces the spin effects but also enhances the combustion process in two locations with two different mechanisms. The first location in which enhancement occurs is at the cumbustor inlet, through the mechanism of swirling flow. The second locaton in which enhancement occurs is at the combustor exit, through the mechansism of added mixing of the unburned fuel, incomplete combustion products, and the pure air core.